Temperature-dependent of sub-threshold slope of AlGaN/GaN MOSHFETs with HfO2 gate oxide prepared by ALD

The sub-threshold slope (SS) of AlGaN/GaN MOSHFETs with HfO
₂
gate oxide prepared by Atomic Layer Deposition (ALD) were investigated. The different SS values, like as 290 mV/dec and 100 mV/dec for MOSHFETs with and w/o oxygen-plasma pre-treatment (PHf- and Hf-MOS) respectively, were estimated. The analysis were realized in temperature range from RT to 300°C. From SS, the average Dit, like as 8.4×10
¹²
eV
¹
cm
^-2
and 1.5×10
¹²
eV
^-1
cm
^-2
for Hf-and PHf-MOS, respectively, were evaluated. The gate leakage current has a strong effect on the SS. The gate leakage were reduced about two orders of magnitude for PHf-MOS (~10
^-8
A/mm at -10V) with oxygen-plasma pre-treatment. The improved SS obviously is also due to the large I
_ON
/I
_OFF
ratio (10
⁸
). An increase of SS values with temperature, were found. However, the PHf-MOS have exhibited an approximately half angle of slope of SS with temperature (0,37mV/°C) than Hf-MOS (0,63mV/°C). As a result from SS the D
_it
for PHf-MOS were reduced approximately five times.